I have no idea what else that material is called, but it's insanely strong. individual strands are dangerous (though not actually monomolecular as the name would imply), but it's used for other things too. You can get super thin rope that you have to have special gloves to handle under tension for instance---it's made from the same stuff, just woven into thicker cables.

Well, regardless of the actual material the net is made of, using a net is kind of difficult. It requires an exotic ranged weapon skill and I don't think anyone has training with nets. Also kind of hard to paint magical sealing sigils on the side of a net.

There is also a net gun which can shoot either a basic net or an electrified version. The gun still requires an exotic ranged weapon skill, but has a longer range than throwing the net.